While major operating systems support UDF, they can all be a little picky about how it's used on a usb or harddrive. And windows has a tendency of not mounting

While major operating systems support UDF, they can all be a little picky about how it's used on a usb or harddrive. And windows has a tendency of not mounting something you didn't unmount properly (plugging it into a linux machine fixes this, from my experience). The main problem you have is that there is no udf partition id, so I've never had it mount on OSX systems I've had access to (I have none myself, and it seems to respect the partition id, unlike windows and linux). This post seems like a good summary, http://tanguy.ortolo.eu/blog/article93/usb-udf http://tanguy.ortolo.eu/blog/article93/usb-udf. Though be warned that (from a quick read) some of the comments contain some misinformation.